This invention relates to a tubular frame.
The honeycomb is well known in the natural environment and its advantage in strength:weight ratio is well documented.
The strength:weight ratio factor is an ongoing problem in the aeroplane and aerospace industries. The greatest percentage of commercial aeroplane structural weight is that of the main airframe structure and skin structure combined so it is in that area that an improvement is sought. The type of commercial aeroplane fuselage structures in use at present is mainly frame and stringer covered by a skin. Another fundamental problem in an aeroplane structure is that of metal fatigue caused mainly by compound fluctuations leading to weakening, cracking, or even total failure.
U.S. Pat. No. 4674712 discloses a composite material aeroplane having a double-lobe fuselage cross-section. The fuselage comprises a double-lobe shell, an interior vertical plane centreline web, and an interior platform supported centrally by the web, all formed of composite panels comprised of graphite honeycomb cores with biasplied layers of graphite fibre skins.
CH-A-571130 discloses a skeleton suitable for the construction of factory and warehouse buildings, which can be assembled from individual, lightweight, compact, structural components. The skeleton can be in the form of part of a sphere or part of a cylinder. The components are in the form of polygonal frames which are assembled together to provide a honeycomb-form skeleton. A major advantage is stated to be that the individual components are relatively inexpensive to manufacture and can conveniently be transported to the construction site where they can readily be connected together.
According to the present invention, there is provided a tubular frame, characterized in that said frame comprises a honeycomb structure with cells thereof distributed round the periphery of the frame and distributed along the frame, and in that said cells are each of at least five-sided form and the sides thereof are provided by elongate structural elements which lie within the periphery of the frame and the length directions of which are peripheral of the cells.
Owing to the invention, the tubular frame can be of greater strength than if comprised of a honeycomb structure consisting of rectangular cells. The present frame has superior axial, torsional and lateral stiffness, so as to make a more rigid structure whereby the factors that cause metal fatigue can be reduced.
It is possible to re-locate some of the loadings and look at the design criteria from a different aspect by introducing the present stronger, more rigid structure of a configuration better suited to perform its function and a better method of manufacture.
The present invention is applicable to airframes, bridge structures, pressure vessels, model aircraft, coffer dams, ship hulls, tubular reinforcing, packaging, columns and beams, axles and pre-fabricated buildings.